American Standard AUD1B080A9H31A Error Code 9 Flashes: Igniter Circuit / Grounding Fault
What Does Code 9 Flashes Mean?
Code 9 (9 Flashes) on the American Standard AUD1B080A9H31A indicates a problem with the igniter circuit, possibly combined with an electrical grounding issue. The hot surface igniter is the component that heats up to ignite the gas burners, and without a functioning igniter circuit, the furnace cannot safely start combustion.
The most common cause is a failed hot surface igniter. These ceramic components (silicon carbide or silicon nitride) degrade over time from repeated thermal cycling — heating to approximately 1800 degrees Fahrenheit and cooling back down thousands of times. Eventually they crack or develop an internal break. A failed igniter will not glow during the startup sequence.
This code also checks for a grounding problem. Specifically, the voltage between the line neutral (N) and the 24VAC common should be 2 volts or less. If this voltage is too high, it indicates a grounding issue that can interfere with the igniter circuit and flame sensing. A technician with a multimeter needs to test the igniter resistance, check the grounding, and replace any failed components.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Failed hot surface igniter | Most common | ✗ Call a pro → |
| Grounding problem (voltage between N and Common exceeds 2V) | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The furnace shows 9 flashes and the igniter does not glow during startup — the igniter circuit needs professional testing
- A grounding problem is suspected based on intermittent igniter or flame sensor issues
✓ Verified against manufacturer service manual — March 2026